WO2008047121A1

WO2008047121A1 - Apparatus for raising and lowering a load

Info

Publication number: WO2008047121A1
Application number: PCT/GB2007/003967
Authority: WO
Inventors: Kevin Burrows
Original assignee: Sashmatic Limited
Priority date: 2006-10-18
Filing date: 2007-10-18
Publication date: 2008-04-24
Also published as: GB0620779D0

Abstract

Apparatus (200) for raising and lowering a load, and particularly for raising and lowering a sash (14) of a sash window (10) is provided. The apparatus comprises driving means (204, 208, 212, 102) for driving the sash between a raised position and a lowered position and spring means (106) for counterbalancing the weight of the sash. As sash window incorporating such apparatus is also disclosed.

Description

APPARATUS FOR RAISING AND LOWERING A LOAD

[001] The present invention relates to apparatus for raising and lowering a load and, in particular, to apparatus for raising and lowering a sash of a sash window (double-hung window) .

[002] Balances such as the spiral balance of Figure 2 for use with sash windows are known, and serve to assist a user when opening and closing the window by counterbalancing the weight of the sash. As a result, the force that needs to be exerted by the user to raise the sash is reduced. [003] However, in certain circumstances, it is desirable to enable a user to open a window at the touch of a button. This is particularly desirable for elderly or disabled users, or in cases where it is necessary to regularly open and close large numbers of windows, such as in school buildings.

[004] This is typically achieved by providing a motor to open and close the sash windows, so that no effort on the part of the user is required. For example, WO-A-03/012237 discloses a rack and pinion drive used to open and close sash windows .

[005] However, the weight of a sash of a typical sash window means that the motor- and associated drive mechanism required for this purpose are bulky, expensive, and consume a considerable amount of power during operation.

[006] Moreover, in many instances, the stile of the window is not large enough to house the motor and associated mechanism, resulting in an ungainly housing being required in -proximity to the window. [007] It is an object of the present invention to overcome the above problems .

[008] According to one aspect of the present invention there is provided apparatus for raising and lowering a sash of a sash window, the apparatus comprising: - driving means for driving the sash between a raised _ O _

position and a lowered position; and spring means (spring balance means) for counterbalancing the weight of the sash.

[009] Since movement of the sash is driven by the driving means, no effort is required of the user other than, for example, pressing a button to control the driving means.

Moreover, the spring means counterbalances the weight of the sash so that the driving means is not required to bear the weight of the sash, as is the case with the rack and pinion drive of WO-A-03/012237. The spring means thus reduces the power required for driving the sash. As a result the driving means can be made sufficiently compact to fit within the stiles of a standard sash window. In particular, it has been found that the dimensions of the driving means can be made sufficiently small for the driving means to be housed in the casing of a standard unpowered spiral balance, such as that shown in Figure 2. This results in a neat visual appearance when the apparatus of the present invention is installed in a sash window, providing for a more aesthetically pleasing appearance than known arrangements.

Furthermore, because the motor is smaller than that of known motorised sash windows, it is cheaper to install and run, and is more energy efficient.

[0010] The driving means may be arranged substantially concentrically with the spring means. The driving means may be arranged radially within the spring means.

[0011] The term "spring means" or "spring balance means" as used herein refers to a mechanism which uses some form of spring for the purpose of counterbalancing the weight of a load, such as that used in the manual spiral balance of Figure 2.

[0012] In one embodiment, the driving means comprises: - a driving member for attachment to the sash; and a rotational member; wherein the driving member is engaged with the rotational _ ^ _

member such that rotation of the rotational member causes the driving member to move linearly, for driving, the sash between the raised and lowered positions.

[0013] In this embodiment, the rotational member may have a threaded surface for engaging a correspondingly threaded surface associated with the driving member for linearly moving the driving member when the rotational member is rotated.

[0014] In this embodiment, the threaded surface of the rotational member may be provided on an internal surface thereof. The rotational member may be an elongate tube, in which case the threaded surface may be provided on an internal surface of said elongate tube. ^■ [0015] Also in this embodiment, the driving member may be an elongate member. In this case the threaded surface of the driving member may be provided on the external surface of a cylindrical member provided at or adjacent one end of the elongate member. The cylindrical member may be integrally formed as part of the elongate member, may be a sleeve formed around the elongate member, or may extend from the end of the elongate member.

[0016] The elongate member may be engaged with a follower member coupled to the spring means, such that the linear movement of the elongate member causes the follower member to rotate. In this case, the spring means may comprise a torsionally resilient member for resisting relative^' rotation between the follower member and the elongate member in the direction associated with lowering the sash, to thereby counterbalance the weight of the sash. [0017] Accordingly, the spring means assists with relative rotation between the follower member and the elongate member in the direction associated with raising the sash, to assist the driving means in raising the sash. [0018] To this end, the elongate member may have a helical form along at least part of the length thereof, and the follower member may have a correspondingly formed interior surface for engaging with the elongate member. Further, the torsionally resilient member preferably comprises a torsion spring. [0019] In another embodiment, the driving means comprises :- a rotational member; a linearly movable coupling member; and sash attachment means for attachment to the sash and connected to the coupling member; wherein the coupling member is engaged with the rotational member such that rotation of the rotational member causes the coupling member to move linearly for driving the sash attachment^" means between said raised and lowered positions . [0020] In this embodiment, the rotational member preferably has a threaded surface for engaging a correspondingly threaded surface of the coupling member for linearly moving the coupling member when the rotational member is rotated. [0021] The threaded surface of the coupling member may be an internal surface thereof. The coupling member may be tubular. The threaded surface of the rotational member may be an external surface thereof.

[0022] In this embodiment, the apparatus may further comprise: - an elongate member arranged to move linearly in association with the coupling member; and a follower member coupled to the spring means; wherein the elongate member is engaged with the follower member such that linear movement of the elongate member causes the follower member to rotate, and wherein the spring means comprises a torsionally resilient member for resisting relative rotation between the coupling member and the sash attachment means in a direction associated with lowering the sash, to thereby counterbalance the weight of the sash. [0023} Accordingly, the spring means assists with relative rotation between the coupling member and said sash attachment means in the direction associated with raising the sash, to assist the driving means in raising the sash.

[0024] To this end, the elongate member may have a helical form along at least part of the length thereof, and the follower member may have a correspondingly formed interior surface for engaging with the elongate member. Further, the torsionally resilient member may comprise a torsion spring.

[0025] In this embodiment, the follower member may be coupled to the spring means via the coupling member. That is to say, the rotation of the follower member may be conveyed to the spring means by the coupling member. [0026] Thus, the coupling member not only moves linearly along the rotational member to raise and lower the sash, but also rotates about the rotational member, to tension or un- tension the spring means. The coupling member is thus a common coupling member which serves a dual purpose. [0027] The follower member, may be connected to the rotational member such that linear movement, of the follower member relative to the rotational member is prevented, whilst, rotation of the follower member relative to the rotational member is allowed.

[0028] Thus the follower member is free to rotate in accordance with the helical form of the elongate member as this passes therethrough, whilst also being held at a fixed axial position relative to the window frame. Tension in the spring means thus acts on the elongate member through the follower member to resist downward movement of the sash, and thus assists with upward movement of the sash. [0029] The coupling member may be formed with a longitudinal slot along at least part of the length thereof and the follower member may be formed with a corresponding projection. The projection is slidably engaged with the longitudinal slot such that relative rotation of the follower member and the coupling member is prevented, whilst relative linear movement of the follower member and the coupling member is allowed.

[0030] Thus, the projection on the follower member does not prevent the coupling member moving linearly to drive the sash, but does cause the coupling member to rotate when the follower member rotates.

[0031] The coupling member may be made up of more than one element. For example, the coupling member may comprise a slotted tubular element for engagement with the follower member, attached at one end to a nut element for engagement with the rotational member.

[0032] The coupling means may be connected to the sash attachment means (and thus to the sash) via the spring means. This avoids the need for the coupling means to be attached directly to the sash attachment means.

[0033] The elongate member may be located radially within the coupling member and the spring means.

[0034] The rotational member may be an elongate tube. The rotational member may be insertable radially within the coupling member,^' and the elongate member may be insertable radially within the rotational member.

[0035] The apparatus preferably further comprises additional spring means for supporting the weight of the sash. The additional spring means may, in use, be attached at one end thereof to the sash, and at the other end thereof to a frame of the sash window. In the case where the apparatus is provided within a casing, the additional spring means may be attached to the casing, and thus, effectively, to the window frame. The additional spring means may comprise a tension spring.

[0036] This additional spring means is desirable for heavier sashes, and provides additional support for the weight of the sash. In particular, it means that the entire weight of the sash is not borne . at the point of attachment of the rotational member to the motor. Moreover, when combined, the effects of the two springs help produce more linear loading over the whole direction of travel of the spiral balance. This is particularly useful for heavier sashes. [0037] According to another aspect of the present invention, there is provided apparatus for raising and lowering a sash of a sash window, the apparatus comprising: - a rotational member; sash attachment means for attachment to the sash; a linearly movable coupling member connected to the sash attachment means, and engaged with the rotational member such that rotation of the rotational member causes the coupling member to move linearly for driving the sash attachment means to raise and lower the sash; an elongate member arranged to move linearly in association with the coupling member; a rotational follower member engaged with the elongate member such that linear movement of the elongate member causes the follower member to rotate; and a torsionally resilient member coupled to the follower member via the coupling member, for resisting relative rotation between the coupling member and the sash attachment means in a direction associated with lowering the sash, to thereby counterbalance the weight of the sash. [0038] According to another aspect of the present invention, there is provided apparatus for raising and lowering a sash of a sash window, the apparatus comprising:- a rotatable member having a threaded drive section and a rotatable coupling section being rotatable relative to said threaded drive section; an axially moveable coupling coupled to the threaded drive section such that said axially moveable coupling is moveable along the axis of said rotatable member on rotation of said threaded drive section, said axially moveable coupling further being coupled to said rotatable coupling section for preventing relative rotation there between; a sash connector for connection to said sash; a helical rod fixed relative to said sash connector and coupled to said rotatable coupling such that axial movement of said sash connector causes rotation of said rotatable coupling; and a torsionally resilient member for resisting relative rotation between said axially moveable coupling and said sash connector in a direction associated with lowering the sash, to thereby counterbalance the weight of the sash. [0039] The apparatus may further comprise a motor for rotating the rotational member.

[0040] The apparatus may comprise control means for controlling operation of the driving means. [0041] The apparatus may further comprise means for detecting the position of the sash relative to a frame of the window. ^{' ' '}

[0042] , The apparatus may further comprise means for detecting when the movement of the sash is obstructed. [0043] According to another aspect of the present invention, there is provided a sash window comprising apparatus as claimed herein.

[0044] The sash window may comprise two or more apparatuses as claimed herein for opening and closing a sash of the window, wherein the two or more driving means are controlled by control means to act in cooperation with one another to drive the sash.

[0045] According to another aspect of the present invention, there is provided a method of retrofitting a power source to a spiral balance, the spiral balance comprising a casing and an elongate member for attachment to a sash of a sash window, the method comprising the steps of:- providing a motor to a casing of the spiral balancer- providing a first threaded member to the motor; and providing a second threaded member to the elongate member of the spiral balance such that the first and second threaded members engage with one another.

According to another aspect of the present invention, there is provided apparatus for raising and lowering a load, the apparatus comprising: - driving means for driving the load between a raised and a lowered position; and spring (spring balance) means for counterbalancing the weight of the load; wherein the driving means is arranged substantially concentrically with ^' the spring balance means.

[0046] The driving means may be arranged radially within the spring balance means.

[0047] In any embodiment of the present invention, the spring means for counterbalancing the weight of the sash may be pre-tensioned (pre-loaded) for supporting the full weight of the sash at any point between the raised and lowered positions.

[0048] Embodiments, of the present invention will now be described with reference to the accompanying diagrams in which: -

[0049] Figure 1 is a perspective illustration of a sash window;

[0050] Figure 2 is a longitudinal cross-section of a known spiral balance; [0051] Figure 3 is a plan view of a sheath of the spiral balance illustrated in Figure 2;

[0052] Figure 4 is a longitudinal cross-section of a spiral balance according to a first embodiment of the present invention; [0053] Figure 5 is a longitudinal cross-section of a spiral balance according to a second embodiment of the present invention; and

[0054] Figure 6 is a perspective view of the slotted tube of the spiral balance of Figure 5. [0055] In the figures, features common to different figures are given common reference numerals .

[0056] Figure 1 illustrates a sash window 10 having a frame 12 and upper and lower sashes 14, 16 mounted in the frame 12. The frame 12 includes vertical stiles 18 and 20, a cross-member 22 at the top and a sill 24 at the bottom. [0057] Each of the sashes 14, 16 is mounted in a vertical groove (only one of which 26 is visible in Figure 1) and the sashes may move vertically up and down by sliding in these grooves . [0058] Figure 2 illustrates a spiral balance 100 of the type known in the art which operates with the sash window 10 of Figure 1. The spiral balance 100 includes a rod 102 mounted in a sheath (or nut) 104. The sheath 104 is attached to a torsion spring 106 such that it lies coaxially therewith and lies partially within the turns at one end 106a of the spring, and partially emerges from that end. The torsion spring 106 is mounted within a hollow tubular casing 108, and is attached to the casing at an opposite end of the spring 106b. The casing 108 has an inwardly extending circular lip 111 which engages with a correspondingly formed circular groove 109 around the side of the sheath 104 in the portion thereof which emerges from the end of the torsion spring. Thus, the sheath is restrained from linear movement with respect to the casing 108. However, the engagement of the lip 111 in the groove 109 allows for rotational movement of the sheath 104 relative to the casing 108. The casing 108 extends beyond the end 106b of the torsion spring. A frame attachment means 110 for attaching the balance 100 to the

' window frame is inserted in this end of the casing. The frame attachment means 110 is formed to fit tightly within the end of the casing, and has a protrusion of narrower cross section which lies within the turns of the torsion spring 106 in the region of the end 106b thereof.

[0059] Figure 3 illustrates the sheath 104 in plan view. The sheath is formed with a helical hole 114 which extends along the longitudinal axis thereof for receiving a helical section 112 of the rod 102. The helical section 112 of the rod 102 and the hole 114 are formed so that the sheath rotates relative to the rod as the rod moves back and forth in the directions indicated by arrow 118 in Figure 2. That is to say, the sheath 104 acts as a follower member for the rod 102. The hole 114 is typically of substantially square cross-section, with nodules formed on the internal surfaces thereof, for locating on the flat surfaces of the helical section 112 of the rod 102. This allows for changes in pitch of the helical section 112 of the rod 102. [0060] The use of the spiral balance 100 will now be described with reference to sash 14 of the sash window 10 illustrated in Figure 1. The frame attachment means 110 is attached to the cross-member 22 by means which will be readily apparent to those skilled in the art. The rod 102 is attached at an end 102a thereof to points on the side of sash 14, whilst the sash is in its closed (or raised) position. The means by which the rod 102 is attached to the sash 14 will be readily apparent to those skilled in the art. Neither the attachment of the frame attachment means 110 to the cross-member 22 or the rod 102 to the sash 14 permits rotation of the rod or frame attachment relative to their respective attachment points. However, the attachment of the rod 102 to the sash 14 may permit pivotal movement of the sash relative to the rod to allow tilting of the sash 14.

[0061] As the sash 14 is lowered and raised, the rod 102 is caused to move linearly with respect to the sheath 104 (in the directions indicated by arrow 118) . The interaction of the helical section 112 of the rod 102 and the helical hole 114 of the sheath causes the sheath 104 to rotate relative to the casing 108 as the sash 16 is lowered and raised. Since the sheath 104 is attached to the end 106a of the torsion spring 106, the rotation of the sheath 104 in turn causes the tension in the spring to increase or decrease, depending on the direction of rotation.

[0062] The arrangement of the torsion spring 106 is such that downward movement of sash 14 (to move it to its lowered or open position) acts against the bias of the spring 106, whilst upward movement of the sash 16 (to return the sash to its raised or closed position) acts with the bias of the spring 106. Thus, the downward movement of the sash 14 causes the rod 102 to be drawn outwards from the casing 108, thereby rotating the sheath 104 to increase the tension (load) in the torsion spring. The subsequent upward movement of the sash 14 is assisted by this tension in the torsion spring 106, which acts through the sheath 104 on the helical section 112 of the rod 102, to urge the rod 102 to withdraw into the casing. This has the effect of substantially counterbalancing the weight of the sash 14, significantly reducing the effort involved in raising the sash than if the entire weight of the sash were to be lifted, and also to hold the window in place at any open position. [0063] Typically, during installation, the rod will be rotated before attachment to the sash 14 in its closed position, in order to pre-tension (pre-load) the spring.

[0064] The helical section 112 of the spiral rod 102 is generally manufactured with a graduated spiral to ensure linear loading of the torsion spring.

[0065] The present invention draws on the principles of the known spring balance system to achieve a powered system which eliminates the need for the user to exert any force in raising or lowering the sashes of a sash window. At the same time, the requirement for bulky, expensive and high power consuming equipment seen with previously known motorised systems is avoided.

[0066] Figure 4 illustrates a spiral balance 200 according to a first embodiment of the invention for use with the sash window of Figure 1 in place of the manual spiral balance of Figure 2. Features common to the manual spiral balance of Figure 2 and the present embodiment are given common reference numerals.

[0067] The spiral balance 200 has a casing 108 and a frame attachment means 202 for attaching to the frame of the sash window, for example, to the cross-member 22 illustrated in Figure 1. In the embodiment of Figure 4, the space occupied by the frame attachment means 110 in the spiral balance of Figure 2 is occupied by a smaller frame attachment means 202, the remaining space being occupied by a motor and a gearbox 204. The motor 204 is kept in place by a retainer 206 which is attached to the internal walls of the casing 108 and abuts the end wall of the motor 204. [0068] As with the spiral balance of Figure 2, the spiral balance 200 is provided with a rod 102, a sheath 104 and a torsion spring 106.

[0069] As with the spiral balance of Figure 2, during installation, the rod will typically be rotated before attachment to the sash 14 in its closed position, in order to pre-tension (pre-load) the spring.

[0070] In addition to these elements, a tube 208 lies coaxially (concentrically) with and radially within the turns of the torsion spring 106 and is engaged at one end thereof with the motor 204 by means of a drive collar 210. [0071] The rod 102 is formed with a sleeve 212 around a portion of the helical section 112 of the rod, near the end 102b of the rod which lies within the casing 108. The sleeve 212 is formed such that the rod 102 can not rotate relative thereto, and may be integrally formed with the rod. [0072] The tube 208 is formed with a helical thread on its inner surface, which engages with a corresponding thread formed on the outer surface of the sleeve 212. [0073] The rod 102 is prevented from rotating through its attachment to the sash. Thus, as the motor 204 rotates the tube 208, the rod 102 is caused to move into or out of the casing 108 in the directions indicated by arrows 214

(depending on the direction of rotation of the motor 204).

[007^*4] This linear movement of the rod 102 recreates the movement generated by manual movement of the sashes with the manual spiral balance of Figure 2. Thus, the principles of the spiral balance described above in relation to Figure 2 apply equally to this embodiment of the invention- That is to say, when attached to the sash window of Figure 1 in the same way as described for the manual spiral balance, operating the motor 204 to drive the rod 102 causes the rod 102 to move linearly with respect to the sheath (follower member) 104 (in the directions indicated by arrow 214) . The interaction of the helical section 112 of the rod 102 and the helical hole 114 of the sheath causes the sheath 104 to rotate relative to the casing 108 as the sash 16 is lowered and raised. Since the sheath 104 is attached to the end 106a of the torsion spring 106, the rotation of the sheath 104 in turn causes the tension in the spring to increase or decrease, depending on the direction of rotation. [0075] The arrangement of the torsion spring 106 is such that driving the rod 102 to achieve a downward movement of sash 14 acts against the bias of the spring .106, whilst driving the rod 102 to achieve an upward movement of the sash 16 acts with the bias of the spring 106. The downward movement of the sash 14 corresponds to the rod 102 being drawn outwards from the casing 108, thereby rotating the sheath 104 to increase the tension (load) in the torsion spring. The subsequent upward movement of the sash 14 is thus assisted by this tension in the torsion spring 106, which acts through the sheath 104 on the helical section 112 of the rod 102, to urge the rod 102 to withdraw into the casing. This has the effect of substantially counterbalancing the weight of the sash 14, significantly reducing the power required for raising the sash than if the entire weight of the sash were to be lifted, and also to hold the window in place at any position in which the movement is stopped.

[0076] The threaded tube 208 of the embodiment of Figure 2 is preferably between 300mm and 1000mm in length, and is preferably provided with a continuous thread substantially along its entire length.

[0077] Figure 5 illustrates a spiral balance 300 according to a second embodiment of the present invention, for use with the sash window of Figure 1 in place of the manual spiral balance of Figure 2. Features common to this second embodiment and the. known spring balance of Figure 2 (and/or the embodiment of Figure 4) are given common reference numerals . [0078] The spiral balance 300 of Figure 5 has a casing 108 and a frame attachment means 202 for attaching to the frame of the sash window, for example, to the cross-member 22 illustrated in Figure 1. As with the embodiment of Figure 4, the frame attachment means 202 occupies a smaller space than the frame attachment means 101 of Figure 2, the remaining space being occupied by a motor and a gearbox 204. The motor 204- is kept in place by a retainer 302 which is attached to the internal walls of the casing 108, and abuts the end wall of the motor 204. [0079] A drive tube 304 is located longitudinally within the casing 108 and is engaged at one end thereof with the motor 204 by means of a drive collar 210. Thus, the drive tube can be rotated by the motor, but can not move axially relative to the motor or the casing. The drive tube is formed with a helical thread on its outer surface, along substantially the full length of the tube. A nut 306 is formed with a corresponding helical thread on its inner surface, and is threaded onto the drive tube. The internal threaded surface of the nut engages with the external thread of the drive tube, such that rotation of the drive tube causes the _.nut to move axially back and forth along the length of the tube when rotation of the nut is restricted.

[0080] The nut 306 is attached at the end further from the motor 204 to an end 308a of another tube (slotted tube 308) , formed with a longitudinal slot 309 along substantially the entire length thereof (see Figure 6) , which tube is also located longitudinally within the casing 108. The attachment of the nut to the slotted tube is such that the nut can not rotate relative to the slotted tube, or move axially with respect to the slotted tube. Thus, as the nut moves back and forth along the length of the drive tube 304, the slotted tube also moves back and forth. The slotted tube lies coaxially with the drive tube, and has an internal diameter slightly larger than the largest external diameter of the drive tube, such that the drive tube can pass into the hollow interior of the slotted tube as the nut moves along the drive tube towards the motor 204.

[0081] The opposite end 308b of the slotted tube 308 (the end_. further from the motor 204) is attached to a cylindrical section 310a of a sash attachment means 310, in such a way that the slotted tube and the sash attachment means can not move axially apart (although the slotted tube can rotate relative to the sash attachment means) . Thus, as the nut 306 and the slotted tube 308 move back and forth relative to the casing 108, the sash attachment means also moves back and forth, ie, in the direction indicated by arrows 311.

[0082] The sash attachment means 310 has four integrally formed cylindrical sections 310a, b, c and d of successively larger circular cross-section. The cylindrical section 310a to which the slotted element is attached has the smallest diameter. At the opposite end of the sash attachment means, the cylindrical section 310a has the largest diameter. This diameter is slightly smaller than the internal diameter of the casing 108. Thus the sash attachment means 310 is free to slide within the casing 108. To enable the sash attachment means to pass into and out of the casing 108, the spiral balance 300 of the present embodiment may lack the lip 111 of the manual spiral balance of Figure 2. Alternatively, the casing 108 may extend over substantially the full length of the sash window, in order to guide the sash attachment means over the full extent of its movement.

[0083] The sash attachment means 310 incorporates means that will be readily apparent to those skilled in the art for attaching the spring balance to the sash to be raised or lowered. It should be noted that when attached to the sash, the sash attachment means can not rotate relative to the casing 108.

[0084] Due to the arrangement described above, when rotation of the nut 306 relative to the casing 108 is restricted, rotation of the drive tube 304 by the motor 204 causes the nut 306, and thus the slotted tube 308 and 'the sash attachment means 310 to move in the directions indicated by the arrows 311. It is this axial back and forth movement which, in use, raises and lowers the sash to open and close the window. [0085] As with the manual spiral balance of Figure 1 and the previous embodiment, the spiral balance 300 of Figure 5 comprises a rod 102 which lies longitudinally within the casing 108, and which is formed with a helical section 112 along at least part of its length. In the present embodiment, the end 102a of the rod is molded within the sash attachment means 310, so that it can not move either axially or rotationally relative to the sash attachment means. Accordingly, when the sash moving means is moved back and forth to raise and lower the sash, as described above, the rod 102 is also caused to move back and forth relative to the motor 204 and the casing 108.

[0086] Similarly to the manual spiral balance of Figure 2 and the previous embodiment, the spiral balance 300 has a sheath which acts as a follower member for converting linear movement of the rod 102 into' rotational movement. However, unlike the previously described spiral balances 100, 200, the follower member 312 of the present embodiment is provided inside the slotted tube at an end 304a (the end further from the motor 204) of the drive tube 304. The follower member is mounted to the end of the drive tube by means of a swivel 314, such that the follower member can rotate but can not be displaced axially with respect to the drive tube. The rod 102 extends from the sash attachment means, through the slotted tube 308, through a helical hole in the follower member 312, and terminates with its end 102b located within the drive tube 304.

[0087] The follower member 312 is similar to the sheath 104, in that the helical hole in the follower member is formed to cooperate with the helical section 112 of the rod 102, such that the follower member is caused to rotate as the helical section of the rod passes back and forth therethrough. As with the sheath 104, the hole is typically of substantially square cross-section with nodules formed on the internal surfaces thereof, for locating on the flat surfaces of the helical section 112 of the rod 102, to allow for changes in pitch of the helical section 112 of the rod 102.

[0088] The follower member 312 has a spigot (projection) 316 which extends from inside the slotted tube 308, to engage with the longitudinal slot 309 thereof, such that when the follower member rotates, the slotted tube also rotates. The longitudinal slot is provided to prevent relative rotation between the follower member and the slotted tube, whilst allowing the slotted tube to move axially with respect to the follower member, and thus the drive tube 304 as described above.

[0089] As the sash 14 is raised and lowered via rotation of the drive tube 304, the rod 102 moves back and forth through the follower member 312, which causes the follower member and the slotted tube 308 to rotate relative to both the rod and the drive tube. Since the nut 306 is attached to the end 308a of the slotted tube,, the nut is also caused to rotate around the drive tube. This rotation of the nut around the drive tube is in addition to the rotation of the drive tube within the nut which causes the axial back and forth movement of the nut described above.

[0090] A helical torsion spring 318 similar to the torsion spring 106 of the manual spiral balance of Figure 1 and the previous embodiment is provided for counterbalancing the weight of the sash 14. The torsion spring is arranged concentrically around the rod 102, the follower member 312, the slotted tube 308, the nut 306, and the drive tube 304. The torsion spring is attached at one end to a lip 306a of the nut and at the other end to the second smallest cylindrical section 310b of the sash attachment means 310, such that rotation of the nut in one direction tensions

(loads) the spring, and rotation in the opposite direction releases that tension (unloads) the spring. Thus, unlike the manual spiral balance of Figure 2 and the previous embodiment, the torsion spring 318 moves back and forth with the nut 306 as the sash is raised and lowered. Nevertheless, because the rotation of the rod follower is conveyed to the torsion spring via the slotted tube 308 and the nut 306, the torsion spring 318 acts in the same way as the spring 106 of the manual spiral balance of Figure 2 and the previous embodiment. Accordingly, the principles of the spiral balance described in relation to Figure 2 and the previous embodiment apply equally to this second embodiment of the invention.

[0091] In the arrangement described above, the slotted tube 308 is attached to the sash attachment means 310 so that the axial movement of the nut 306 is conveyed to the sash attachment means via the slotted tube. However, since the torsion spring is also attached to the sash attachment means, provided the torsion spring is selected to be sufficiently axially inextensible, the slotted tube need not be attached to the sash moving means. This is because the axial movement of the nut will be conveyed to the sash moving means via the torsion spring.

[0092] As the motor rotates the drive tube 304, the nut 306 is caused to move linearly (axially) along the drive tube. Since the nut is attached to the end of the slotted tube 308 and the torsion spring 318, these elements are also caused to move linearly. The slotted tube is able to slide over the follower member 312 since the spigot 316 of the follower member is slidably engaged with the longitudinal slot 309 of the slotted tube. The linear movement of the nut is thus conveyed to the sash attachment means 310 (and the sash attached thereto) via the slotted tube and/or the torsion spring, depending on which of these is attached to the sash attachment means.

[0093] At the same time, since the rod 102 is molded within the sash attachment means 310, the rod 102 is also caused to move linearly through the follower member 312, thereby causing the follower member to rotate. Since the spigot 316 of the follower member is engaged with the longitudinal slot 309 of the slotted tube 308, the slotted tube is caused to rotate in synchrony with the follower member. This rotation is, in turn, conveyed to the nut 306, causing it to rotate about the drive tube 304 at the same time as moving axially along the drive tube.

[0094] Since the nut 306 is attached to the end of the torsion spring 318, the rotation of the nut about the drive tube 304 causes the tension in the torβion spring 318 to increase or decrease depending on the direction of rotation. [0095] The arrangement of the torsion spring 318 is such that driving the rod 102 to achieve a downward movement of sash 14 acts against the bias of the spring, whilst driving the rod to achieve an upward movement of the sash acts with the bias of the spring 106. The downward movement of the sash corresponds to the rod 102 being drawn outwards from the casing 108, thereby rotating the sheath 104 to increase the tension (load) in the torsion spring. The subsequent upward movement of the sash is thus assisted by this tension in the torsion spring, which acts through the follower member 312 on the helical section 112 of the rod, to urge the rod in the direction towards the motor 204. This has the effect of substantially counterbalancing the weight of the sash 14, significantly reducing the power required for raising the sash than if the entire weight of the sash were to be lifted, and also to hold the window in place at any position in which the movement is stopped.

[0096] As with the spiral balance of Figure 2, the torsion spring will typically be pre-loaded or pre-tensioned during installation, for example by rotating the rod 102 before attachment to the sash 14 in its closed position.

[0097] The pitch of the helical section of the rod 102 (ie the number of turns per unit length) is significantly smaller than the pitch of the thread of the drive tube 304 and the nut 306. This is true even where the pitch of the helical section of the rod is smallest. Accordingly, the nut 306 rotates relative to the casing significantly more slowly than the drive tube rotates relative to the casing. Thus, the rotation of the nut 306 does not interfere with the linear movement of the nut 306 along the drive tube. [0098] The ratio of the pitch of the helical section of the rod to the pitch of the thread of the drive tube is selected to achieve a desired speed of movement of the sash with the rotation of the drive tube achievable with the motor. This is turn is dependent on the power output of the motor. [0099] In general, the torsion spring described above will be sufficient to counterbalance the weight of the sash.

However, in certain applications, in particular for heavier sashes, additional spring means may be required.

[00100] To this end, the spiral balance 300 of the present embodiment is additionally provided with a tension spring 320. The tension spring 320 is arranged within the casing, radially outside and concentric with the torsion spring. The tension spring is attached at one end to the second largest cylindrical section 310c of the sash attachment means 310, and at the other end to the retainer 302. Thus, the tension spring bears some of the weight of the sash, such that the entire weight of the sash is not borne at the point of attachment of the drive tube 304 to the motor 204. Since the tension spring is attached between the ^'casing and the sash attachment means 310, as the sash attachment means moves back and forth with the sash 14, the tension spring extends and contracts, to assist in counterbalancing the weight of the sash. Thus, in use, when the sash is moved in the direction towards the motor, this movement is further assisted by the unloading of tension in the tension spring 320.

[00101] It will be appreciated that, in practice, the balance would be required to be installed in the upper portion of the sash window frame, such that the tension spring 320 is stretched as the sash is moved downwards, so that the upward movement of the sash is assisted by the unloading of the tension spring.

[00102] Thus, both the torsion spring 318 and the tension spring 320 will assist in counteracting the weight of the sash window during lifting and lowering.

[00103] In particular, the use of a torsion spring and a tension spring in combination will result in a more linear loading over the whole travel .of the spiral balance. This can be important for heavier sashes. The graduated helical form of the spiral rod has an increased pitch at the lower section compared with the upper section. This results in an approximately linear loading over the whole travel between the raised and lowered positions. However, in some cases, the upward force produced by the spiral rod can be more pronounced as the balance gets closer to the raised position. In contrast, the force produced by the tension spring becomes

^■ more pronounced as it extends. When combined, the two springs produce an approximately linear upward force in the balance. Thus, as the balance starts to extend from the

5 raised position, the torsion spring does most of the work.

The work done by the torsion spring diminishes as the balance extends. Also, as the balance extends, the tension spring does . more of the work as it extends closer to the fully lowered position. 0 [00104] It will be appreciated that the above described arrangement relies on rotation of the nut 306 relative to the casing 108 being "restricted", such that the nut is caused to move axially along the drive tube 304 when the drive tube is rotated. That is to say, the nut does not simply sit on5 the drive tube and rotate therewith. However, the term "restricted" in this context should not be taken to imply that rotational movement of the nut relative to the casing 108 is totally prevented. Rather, the nut is able to rotate relative to the casing, but only to the extent that the0 follower member 312 rotates as the rod 102 moves therethrough. The "restriction" of the rotation of the nut is thus achieved through the interaction of the helical section 112 of the rod with the helical hole of the rod follower. ' 5 [00105] This works because the pitch of the helical section 112 of the rod 102 is significantly smaller than the pitch of the thread of the drive tube 304 and the nut 306, as discussed in more detail above.

[00106] With either of the embodiments described above,0 the interaction of the driving means for raising and lowering the sash, means that a motor which is small enough to fit within the space occupied by the frame attachment means of conventional spiral balances is more than adequate to provide power for raising and lowering the sashes of typical sash5 windows. Consequently, to install a spiral balance embodying the present invention to a sash window requires no adaptation of the sashes or the windows. It is thus straightforward to fit a device embodying the' present invention to existing spiral balance operated sash windows. [00107] In practice, in a sash window fitted with one or more manual spiral balance mechanisms, it is straightforward to exchange each of the one or more manual spiral balance (s) for a mechanism embodying the present invention, which can be made to have the same, fittings as previous manual spiral balance mechanisms.

[00108] Moreover, the motor is hidden within the existing spring balance mechanism, resulting in a neat visual appearance.

[00109] Furthermore, the power consumed by the motor during operation is low compared to known motorised systems.

[00110] Also with the present invention, the electronic controls for controlling operation of the apparatus may be made sufficiently small to be hidden within the framework of the window. [00111] As with the manual spring balance of Figure 2, during installation, the rod may be rotated before attachment to the sash 14 in its closed position, in order to pretension (pre-load) the spring. [00112] The tension spring 320 of the spiral balance of figure 5 may also be pre-tensioned.

[00113] In both embodiments, the helical section 112 of the spiral rod 102 is generally manufactured with a graduated spiral to ensure linear loading of the torsion spring 106, 318. [00114] The spring balance 100 of Figure 2 can be converted to the spring balance 200 of Figure 4 by removing the frame attachment 110, the rod 102 and the sheath 104. The rod 102 is provided with a threaded sleeve 212 by a suitable method. A threaded tube 208 is inserted into the casing 108 and a motor is attached to the tube 208 by means of a drive collar 210. The motor is then installed into the casing 108 by attaching the retainer 206 to the casing 108 and the motor 204.

[00115] The rod is reinserted into the casing 108 by engaging the thread of sleeve 212 with the thread of the tube 208. Finally, the sheath 104 is reinstalled by attaching it to the torsion spring 106.

[00116] The present invention has been described in terms of a simple spiral balance. However, it will be appreciated that the present invention may equally be applied to more complex spiral balance mechanisms. For example more than one torsion spring may be provided, or additional tension springs may be provided.

[00117] In selecting suitable springs for use with the present invention, springs having similar properties to those used in a corresponding manual spiral balance mechanism may be appropriate.

[00118] The present invention has been described in the context of the upper sash of a sash window, which is lowered to open the window and raised to close the window. However it will be appreciated that with appropriate pre-tensioning of the balance, the invention could be used with the lower sash of a sash window, which is raised to open the window, and lowered to close the window. [00119] More generally, although the present invention has been described in the context of sash windows, it will be appreciated that the invention could be used for raising and lowering loads other than the sashes of sash windows.

Claims

1. Apparatus for raising and lowering a sash of a sash window, the apparatus comprising: - driving means for driving the sash between a raised position and a lowered position; and spring means for counterbalancing the weight of the sash.

2. Apparatus , as claimed in claim 1 wherein the driving means is arranged substantially concentrically with the spring means.

3. Apparatus as claimed in claim 1 or 2 wherein the driving means is arranged radially within the spring means.

4. Apparatus as claimed in any preceding claim wherein, the driving means comprises :- a driving member for attachment to the sash; and a rotational member; wherein the driving member is engaged with the rotational member such that rotation of the rotational member causes the driving member to move linearly, for driving the sash between the raised and lowered positions.

5. Apparatus as claimed in claim 4 wherein the rotational member has a threaded surface for engaging a correspondingly threaded surface associated with the driving member for linearly moving the driving member when the rotational member is rotated.

6. Apparatus as claimed in claim 5 wherein the threaded surface of the rotational member is provided on an internal surface thereof.

7. Apparatus as claimed in any one of claims 4 t^'o 6 wherein the rotational member is an elongate tube.

8. Apparatus as claimed in claim 7 as dependent on claim 5 wherein the threaded surface is provided on an internal surface of said elongate tube.

9. Apparatus as claimed in any one of claims 4 to 8 wherein the driving member is an elongate member.

10. Apparatus as claimed in claim 9 as dependent on claim 5 wherein the threaded surface of the driving member is provided on an external surface of a cylindrical member provided at or adjacent one end of the elongate member.

11. Apparatus as claimed in claim 9 or 10 wherein the elongate member is engaged with a follower member coupled to the spring means, such that the linear movement of the elongate member causes the follower member to rotate.

12. Apparatus as claimed in claim 11 wherein the spring means comprises a torsionally resilient member for resisting relative rotation between the follower member and the elongate member in the direction associated with lowering the sash, to thereby counterbalance the weight of the sash.

13. Apparatus as claimed in claim 11 or 12 wherein the elongate member has a helical form along at least part of the length thereof, and the follower member has a correspondingly formed interior surface for engaging with the elongate member.

14. Apparatus as claimed in any one of claims 11 to 13 wherein the torsionally resilient member comprises a torsion spring.

15- Apparatus as claimed in any one of claims 1 to 3 wherein the driving means comprises :- a rotational member; a linearly movable coupling member; and sash attachment means for attachment to the sash and connected to the coupling member; wherein the coupling member is engaged with the rotational member such that rotation of the rotational member causes the coupling member to move linearly for driving the sash attachment means between said raised and lowered positions.

16. Apparatus as claimed in claim 15 wherein the rotational member has a threaded surface for engaging a correspondingly threaded surface of the coupling member for linearly moving the coupling member when the rotational member is rotated.

17. Apparatus as claimed in claim 16 wherein the threaded surface of the coupling member is an internal surface thereof.

18. Apparatus as claimed in any one of claims 15 to 17 wherein the coupling member is tubular.

19. Apparatus as claimed in any one of claims 16 to 18 wherein the threaded surface of the rotational member is an external surface thereof.

20. Apparatus as claimed in any one of claims 15 to 19 further comprising: - an elongate member arranged to move linearly in association with the coupling member; and a follower member coupled to the spring means; wherein the elongate member is engaged with the follower member such that linear movement of the elongate member causes the follower member to rotate, and wherein the spring means comprises a torsionally resilient member for resisting relative rotation between the coupling member and the sash attachment means in a direction associated with lowering the sash, to thereby counterbalance the weight of the sash.

21. • Apparatus as claimed in claim 20 wherein the elongate member has a helical form along at least part of the length thereof, and the follower member has a correspondingly formed interior surface for engaging with the elongate member.

22. Apparatus as claimed in claim 20 or 21 wherein the torsionally resilient member preferably comprises a torsion spring.

23. Apparatus as claimed in any one of claims 20 to 22 wherein the follower member is coupled to the spring means via the coupling member.

24. Apparatus as claimed in any one of claims 20 to 23 wherein the follower member is connected to the rotational member such that linear movement of the follower member relative to the rotational member is prevented, whilst rotation of the follower member relative to the rotational member is allowed.

25. Apparatus as claimed in claim 24 wherein the coupling member is formed with a longitudinal slot along at least part of the length thereof and the follower member is preferably formed- with a^' corresponding projection, and wherein the projection is slidably engaged with the longitudinal slot such that relative rotation of the follower member and the coupling member is prevented, whilst relative linear movement of the follower member and the coupling member is allowed.

26. Apparatus as claimed in any one of claims 20 to 25 wherein the elongate member is preferably located radially within the coupling member and the spring means.

5 27. Apparatus as claimed in any one of claims 20 to 26 wherein the rotational member is an elongate tube, the rotational member is insertable radially within the coupling member, and the elongate member is insertable radially within the rotational member. 10

28. Apparatus as claimed in any one of claims 15 to 27 wherein the coupling member is made up of more than one element .

15 29. Apparatus as claimed in any one of claims 15 to 28 wherein the coupling means is connected to the sash attachment means via the spring means.

30. Apparatus as claimed in any one of claims 15 to 29, 20 further comprising additional spring means for supporting the weight of the sash.

31. Apparatus as claimed in claim 30 wherein the additional spring means is, in use, attached at one end

25 thereof to the sash, and at the other end thereof to a frame of the sash window.

32. Apparatus as claimed in claim 30 or 31 wherein the additional spring means comprises a tension spring.

30

33. Apparatus for raising and lowering a sash of a sash window, the apparatus comprising: - a rotational member; sash attachment means for attachment to the sash; 35 a linearly movable coupling member connected to the sash attachment means, and engaged with the rotational member such that rotation of the rotational member causes the coupling member to move linearly for driving the sash attachment means to raise and lower the sash; an elongate member arranged to move linearly in association with the coupling member; a rotational follower member engaged with the elongate member such that linear movement of the elongate member causes the follower member to rotate; and a torsionally resilient member coupled to the follower member via the coupling member, for resisting relative rotation between the coupling member and the sash attachment means in a direction associated with lowering the sash, to thereby counterbalance the weight of the sash.

34. Apparatus for raising and lowering a sash of a sash window, the apparatus comprising: - a rotatable member having a threaded drive section and a rotatable coupling section being rotatable relative to said threaded drive section; an axially moveable coupling coupled to the threaded drive section such that said axially, moveable coupling is moveable along the axis of said rotatable member on rotation of said threaded drive section, said axially moveable coupling further being coupled to said rotatable coupling section for preventing relative rotation there between; a sash connector for connection to said sash; a helical rod fixed relative to said sash connector and coupled to said rotatable coupling such that axial movement of said sash connector causes rotation of said rotatable coupling; and a torsionally resilient member for resisting relative rotation between said axially moveable coupling, and said sash connector in a direction associated with lowering the sash, t'o thereby counterbalance the weight of the sash.

35. Apparatus as claimed in any preceding claim further comprising a motor for rotating the rotational member.

36. Apparatus as claimed in any preceding claim further comprising control^' means for controlling operation of the driving means.

37. Apparatus as claimed in any preceding claim further comprising means for detecting the position of the sash relative to a frame of the window.

38. Apparatus as claimed in any preceding claim further comprising means for detecting when the movement of the sash is obstructed.

39. A sash window for opening and closing a sash of the window, comprising apparatus as claimed in any preceding claim.

40. A sash window comprising two or more apparatuses as claimed in any one of claims 1 to 38, for opening and , closing a sash of the window, wherein the two or more driving means are controlled by control means to act in cooperation with one another to drive the sash.

41. A method of retrofitting a power source to a spiral balance, the spiral balance comprising a casing and an elongate member for attachment to a sash of a sash window, the method comprising the steps of:- providing a motor to a casing of the spiral balance; providing a first threaded member to the motor; and providing a second threaded member to the elongate member of the spiral balance such that the first and second threaded members engage with one another. * ,

42. Apparatus for raising and lowering a load, the apparatus comprising: - driving means for driving the load between a raised and a lowered position; and

5 spring means for counterbalancing the weight of the load; wherein the driving means is arranged substantially concentrically with the spring balance means.

10 43. Apparatus as claimed in claim 42 wherein the driving means is arranged radially within the spring balance means.

44. Apparatus for raising and lowering a sash of a sash window, substantially as hereinbefore described with

15 reference to figures 1 and 3 to 6 of the accompanying drawings .

45. A sash window substantially as hereinbefore described with reference to figures 1 and 3 to 6 of the accompanying

20 drawings.

46. Apparatus for raising and lowering a load, substantially as hereinbefore described with reference to figures 1 and 3 to 6 of the accompanying drawings.

25

47. A method of retrofitting a power source substantially as hereinbefore described with reference figures 1 and 3 to 6 of the accompanying drawings.